ML19241A950

LER 79-020/03L-0 on 790525:quarterly MSIV Closure Timing Surveillance Performed & MSIV Closed in 6-s Instead of 5-s. Caused by Varied Speed Control Valve Adjustment on Hydraulic Cylinder

ML19241A950
Person / Time
Site:	Quad Cities
Issue date:	06/20/1979
From:	Dunesia Clark COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19241A947	List: ML19241A946 ML19241A950
References
LER-79-020-03L-02, LER-79-20-3L-2, NUDOCS 7907110462
Download: ML19241A950 (3)

Text

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EN ENT DATE 74 75 RE *C A T O ATE iJ OOC *. E T h.YB E A *,d EVENT CESL9lPTION A*.O PRC8 ABLE CCNsECUE".CES h oi: 1Ouring a Unit one condenser maintenance outace. the cuary 1- "IV clnwra - i-i m o 3j j surveillance (QOs 250-4) was performed. While cerforminn the test, min s t Nm I o la L i solation valve (Msi") A0 1-203-2c closed in 6 seconds. This time exceeds the I o < lmaximun closuru time of 5 seconds for any MslV as stated in T.S. Table 3.7-1. The l

, lseven remaining MslVs were tested satisfactority. I Cl l l I _J 7 8 ) 60 SYSTEM CAUSE CALSE COVP VALVE CCCE COCE SLBCCCE CCYPCNENT CODE SLdCCOE SUBCOCE

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1. LER Number LER/R0 79-20/03L-0

11. L_lCENSEE NAME COMMONWE..LTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION lit. F Af. l L I TV NAME UNIT ONE IV. DOCKET NUMBER 050-254 V. EVENT DESCRIPTION On May 25, 1979, during a Unit One condenser maintenance outage, the quarterly MSIV closure timing surveillance (QOS 250-4) was performed.

While performing the test, main steam isolation valve (MSIV) A0-1-203-2C closed in 6 seconds. This time exceeds the maximum closure time of 5 seconds for any MSIV as stated in Technical Specification Table 3.7-1.

The seven remaining MSlVs were tested satisfactorily. The 2C MSIV will be retimed prior to unit Startup.

There have been two sin llar occurrences in which a MSIV ' ailed to close in less than 5 seconds; the nost recent of which is repcrted in LER/R0 50-254/77-6.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE The main steam isolation valves are required to close in less than five seconds to prevea fuel rod rupture in the event of a steam line break outside the containment. The 2C valve is the outboard primary containment isolation valve in the "C" steam line. The 1C inboard valve closed in 4.9 seconds, which is within the required closure time. The inboard MSIV would have performed as designed to isolate the stean line in less than 5 seconds. Sinc, the redundart valve was operating properly, safe reactor operation was not affected as a result of this occurrence.

Vll, CAUSE The cause of this occurrence is designated as equipment failure.

The speed control valve adjustment on the hydraulic control cylinder had varied, thus slowing down the valve travel time. The control valve is a needle valve that regulates the speed of the hydraulic oil flowing from the bottom to the top of the piston. The piston is attached to the stea of the MSIV to regulate the travel speed of the valve stem.

The speed control unit is manufactured by Flick-Reedy Corp.,

Drawing No. File 4536.

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Vill, CORRECTIVE ACTION The speed control valve was adjusted to speed up th valve closure time. The valve was exercised three times and closed in 3.8 seconds. This corrective action was deemed adequate to prevent reoccurrence.

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